Signal Conditioner - Easy and cheap?

fix the software?

Thanks for the input, I wish it were that simple! Unfortunately, the software is locked / static - no way to make a software correction. I'll go into a little more detail.

This is a wideband O2 sensor. From my reading / testing, the sensor has an output of approximately 0mA during stoichiometric combustion (14.7:1 air fuel ratio), -2mA at the richest condition (11:1 AFR) and about +1.5mA in pure air. It constantly switches from slight positive current flow to slight negative current flow with a response time of about 100 milliseconds, as the computer reads the sensor and tries to keep the combustion at 14.7:1 AFR. For some various tests & experiments I would still like the computer to control the combustion, but do so at different (richer or leaner) conditions than the 14.7:1 which is 'hardwired" in.

My thought was perhaps a simple op-amp circuit which would be capable of offsetting the O2 sensor output slightly to "fool" the computer. For example, if the sensor is setting at 0mA and the circuit could offset it to say -0.3mA the computer would think the combustion is actually rich and pull some fuel out to balance the sensor back to 0mA.

Unfortunately, my mechanical skills are greater than my electronic skills for the time being, so I was hoping someone on the forums might be able to point out a relatively cheap / simple circuit that could do the trick.

Regards, Corey

jasen wrote:

detail always helps.

sounds like ideally something that operates off the automobile's 12V supply would suit, with battery powered a second option.

also voltage in the neighbourhood of 12V

yes sounds like an op-amp based current source could be a good solution. what voltage is on the input to the ECU?

it's possible that going a little leaner will save fuel and increase fuel economy, but it'll shut down the catalytic converter and you'll have emissions problems.

Bye. Jasen